Physics of pruney fingers revealed

An exploration of mathematical shapes could explain why skin gets wrinkled after too much time in the tub.
Understanding the geometry of wrinkly skin could help design new
materials that can stretch out without losing strength.

"The paper explains a mechanism that can explain the structural
stability of keratin in skin and its ability to absorb very large
quantities of water," said mathematician Gerd Schröder-Turk of the University of
Erlangen-Nürnberg in Germany, who was not involved in the new work.
"This is a major breakthrough."

Scientists and frequent bathers know that skin can absorb a
tremendous amount of water, and still be a strong barrier between
our bodies and the harsh outside world.

"Your skin wrinkles, yet it maintains its structure," said
mathematician Myfanwy Evans of the Australian National
University, lead author of the new study. "It doesn't just fall
apart and dissolve into the water."

The skin's resilient stretchiness comes from an intricate
network of fibrous proteins called keratin, which make up the outermost layer of
the skin, as well as hair and nails. Scientists knew that skin's
keratin networks were important, but the arrangement of fibres was
uncertain.

Now, Evans and Australian National University colleague Stephen Hyde may have found a solution. They
describe their stringy skin model in the 8 March Journal of the
Royal Society Interface.

"It explains a lot of mechanical features that hadn't really
been able to be explained before," Evans said.

The researchers stumbled upon the new model in a purely
math-based search for interesting topological shapes. Evans studies
a class of beautiful mathematical shapes called Gyroids, which show up all over the natural
world, from lipid membranes to butterfly wings.

"It's an interesting fusion of maths and experimental science,"
Evans said. "These are popping up everywhere."